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March 16, 2012

Jupiter and Venus, Together

This photo is from the 6th of this month. I took it from near the top of Mt Tolmie. I wanted to try and get a photo with Mercury as well, but the clouds completely blocked it from view. In the picture are Jupiter and Venus. Venus is the lower and brighter of the two white dots. Venus is just nearing its greatest eastern elongation which it will reach on the 27th of March. That is the date when it is the farthest away from the sun in the evening sky, and also the day that it will remain above the horizon the longest. After the 27th it will start appearing closer and closer to the sun until on the 5th and 6th of June it makes a transit of the sun.

Looking through a telescope, you can see that Venus looks like a quarter moon. As the days go on, past the 27th, it will star turning into a sliver and getting smaller and smaller until on the day of inferior conjunction, we cannot see any of the planet illuminated. After that throughout the summer it will get fatter and fatter until on the 15th of August it will be half illuminated again, this time visible in the hours before sunrise. As it continues on, it will continue to get more and more lit up, but it will be going around the sun and getting further and further away and it will get dimmer and closer to the sun once again.

Even with the most advanced telescopes Venus is just a featureless dot. The atmosphere is so thick that to see through it you need to send a space craft there and use radar to map the surface. Venus is so hot and the atmosphere so thick that on the surface there is the same pressure as being a kilometer beneath the ocean on earth at a temperature of 460 degrees celsius. If you had infinite money and resources, you could build cities that floated on the ocean of air at 50km above the surface where the temperature and pressure are just about the same as on earth. Unfortunately, the atmosphere is also made of about 96% carbon dioxide.